Gluconeogenesis is a process of major physiological importance in all species especially in ruminants. The long-term objective of this project is to quantitate the carbon sources contributing to the total glucose utilized by ruminants in various dietary and physiological states. Our "standard" calves, chosen to minimize physiological variables, are 160-205 kg and fed a high-grain ration every 2 hours in amount which will promote slow growth. Our first step was to determine glucose turnover rates which was found to average 655 g/day in these calves. Next, we found that about 60 g of this glucose can be absorbed glucose, indicating that gluconeogenesis must account for over 90% of the glucose utilized. We have estimated in preliminary studies that rumen propionate production averages 579 g/day and that an initial estimate of propionate absorption averages 698 g/day. Preliminary calculations suggest that about 60% of the glucose originates from propionate. During 1977 we will continue to study the contribution of propionate to glucose. We will also begin to study the contributions of amino acids to gluconeogenesis and to study glucose kinetics in lactating goats.